MPs have been heavily criticised by their standards watchdog for dragging their feet over bringing in tougher rules on their behaviour.

Kathryn Hudson, the Parliamentary Standards commissioner, expressed “grave concern” that changes proposed 18 months ago in 2012 had yet to be brought before the House.

The measures were intended to tighten controls on lobbying and declaring interests in the wake of a series of controversies.

MPs with second jobs would also be banned from initiating parliamentary proceedings, such as tabling amendments, in the interests of their employers.

The criticism came months after Patrick Mercer, a Conservative MP, stepped down as MP for Newark days before he was due to be suspended from the Commons for six months.

His decision comes after a joint investigation by The Daily Telegraph and the BBC’s Panorama revealed that Mr Mercer tabled a series of parliamentary questions and put down a motion after accepting a £4,000 from undercover reporters.

Writing in her annual report, Miss Hudson said: “I would be failing in my responsibility to the House if I did not express my grave concern that the House still has not been given the opportunity to consider the revisions to the Guide to the Rules proposed by the Committee on Standards and Privileges in December 2012.

“It is extremely disappointing that time has not been found for such a debate, not least because the new rules are considerably clearer on certain issues, including some which have been the subject of inquiries this year.

“If there is disagreement with some of the Committee’s proposals, MPs would be free to amend them in debate and leadership may be shown by addressing issues transparently and honestly, rather than by avoiding difficult discussions.”

The new code also suggests that MPs should be investigated if their “private and personal” behaviour brings the House into disrepute.

Some believe the latter provision could have been used in the case of former Liberal Democrat Mike Hancock, who has faced no formal censure despite apologising for an “inappropriate and unprofessional” relationship with a vulnerable constituent.

Andrew Lansley, the Tory Leader of the House of Commons, has not yet brought any of the proposals before parliament because he is understood to believe MPs would reject the idea of probes into their private behaviour.

During the year, Miss Hudson said she had “accepted for inqury” nine out of 93 formal complaints to her office.

She said: “These complaints ranged from areas such as failing to register interests or to declare them appropriately, to lobbying for reward.

“They continue to include complaints relating to MPs’ use of the Additional Costs Allowance under the expenses system which ceased in 2010.

“It is to be hoped that we may soon be able to move on from the difficulties of that time.”